Is it normal to to not like anything at all?

I usually try to put up a tough, intimidating front, but really, im just a soft guy. The kind that gets swayed by puss-and-boots puppy-dog eyes.http://www.youtube.com/watch?feature=fvwp&NR=1&v=5Sy0CUy-88Q I dont quite get why or what im feeling right now, and since this is is it normal, I wanted to hear your thoughts.

I noticed that I dont really like anything anymore. I used to have interesting hobbies, and I used to enjoy almost everything I did.

I tried to find positivism in every moment. I dont think that anymore. I cant find enjoyment in anything I do. Its not that I dont try. I always try to find the good in situations, and try to be optimistic. Now, I will not like anything. Nothing, to me, seems to be cool or interesting and I dont know wether this is just myself changing (Im 17.) or if its that ive somehow lost my positivism. (Although I dont see how that could possibly happen.) I really dont see a point to doing anything fulfilling anymore, because life dosent seem to have any worth. This is because productive things in life seem old, boring, and just not worth it anymore. Nothing at all seems worth it anymore, and some days I wish I could just stay in bed and never get up.
(I dont quite know how to tag this because I dont really get what these feelings are or why they are happening to me. Please help me. If you cannot do that, at least let me know what is wrong.)(even though that is kinda helping me.)
is it normal that I feel this way?